Optoelectronic modules, such as a proximity sensors and range imagining cameras, sometimes include at least one channel configured to transmit light to a target, and at least one channel configured to receive light reflected from the target. Further, optoelectronic modules sometimes include a transmissive element, such as an optical element, spectral filter, and/or cover glass placed between the channels and the target. In some cases, transmitted light may reflect from the transmissive element and may cause significant cross talk (e.g., light reflected from the transmissive element is collected by the channel configured to receive light).
Cross talk can produce spurious signals in some cases. For example, an optoelectronic module operable to collect distance information or three-dimensional data via the indirect time-of-flight technique can be affected by spurious signals produced by cross talk emanating from a transmissive element. A signal generated from light reflected from a target and a transmissive element and received by an array of demodulation pixels within a collection channel sometimes includes a component resulting from the target and a component resulting from the transmissive element. Based on the indirect time-of-flight technique, the signal can be converted into a vector having a magnitude corresponding to the signal fidelity (including the transmissive properties of the transmissive element), and a phase ostensibly corresponding to the distance to the target. The phase, however, can be affected strongly by the cross-talk and, in the absence of sufficient calibration data, the corresponding distance data may be inaccurate.
Methods for calibrating the cross talk due to the transmissive element of an optoelectronic module are known, but these methods sometimes require positioning a target at a very large distance (e.g., 10-30 meters or more) from the optoelectronic module. The long distances are often necessary to collect a pure cross talk signal. These methods can be impractical for a manufacturer or even an end user to implement. Accordingly, methods for calibrating and collecting distance data are needed that can be implemented within relatively short distances (e.g., less than a meter) such that a manufacturer or an end user of the optoelectronic module can perform the calibration measurements.